Abstract: A gas turbine engine comprising a variable geometry combustor having fuel injectors, a rich-burn zone, a quick-quench zone, and a lean-burn zone, and further comprising quench ports for admitting quench air to the quick-quench zone; a variable geometry airflow arrangement for the variable geometry combustor, which is configured to vary an airflow through the fuel injectors and/or the quench ports; and a control system configured to control the variable geometry airflow arrangement in dependence upon an airflow delivered to the combustor, a fuel flow to the fuel injectors, and a target index of soot emissions to control the quantity of soot produced by combustion.

Abstract: An aircraft propulsion system includes first and second engines and first and second electrical machines coupled to the first and second engines respectively. The first electrical machine is arranged to be driven by electrical power in order to at least partially drive the first engine. The second electrical machine is arranged to be driven by the second engine to generate electrical power. An electrical network allows transmission of electrical power between the electrical machines. A controller is arranged to selectively reduce fuel flow to the first engine and provide electrical power from the second electrical machine to the first electrical machine to drive the first electrical machine, based on expected properties of contrails formed in an exhaust plume of the first engine and/or the second engine. The system allows the formation of contrails by the engines to be managed in order to mitigate climate-warming effects of the contrails.

Abstract: A power system for an aircraft includes one or more gas turbine engines arranged to burn a fuel so as to provide power to the aircraft; a plurality of fuel tanks each arranged to contain a fuel to be used to provide power to the aircraft; and a fuel manager. At least two of the fuel tanks contain different fuels, which have different proportions of a sustainable aviation fuel. The fuel manager is arranged to store information on the fuel contained in each fuel tank; and to control fuel supply so as to select a specific fuel accordingly to power at least the majority of operations on the ground. The fuel manager may additionally identify which tank contains the fuel with the highest proportion of a sustainable aviation fuel; and that fuel may be used to power at least the majority of operations on the ground.

Abstract: A gas turbine engine for an aircraft includes a staged combustion system having pilot fuel injectors and main fuel injectors. The gas turbine engine further includes a fuel delivery regulator arranged to control delivery of fuel to the pilot and main fuel injectors, and a fuel characteristic determination module configured to determine one or more fuel characteristics of the fuel being supplied to the staged combustion system. A controller is configured to determine a staging point defining the point at which the staged combustion system is switched between pilot-only operation and pilot-and-main operation, the staging point being determined based on the determined one or more fuel characteristics, the controller being configured to control the staged combustion system according to the determined staging point.

Abstract: A combined cycle power generation and storage system is shown. A liquid air energy storage system uses excess power to liquefy air and stores it in a liquid state. A combustion engine produces power by combustion of a carbon-based fuel along with an exhaust stream containing carbon dioxide. A heat recovery system exchanges heat from the exhaust stream to air from the liquid air storage system, and thereby produce a cooled exhaust stream and heated air. An air expansion machine recovers power by expansion of heated air from the heat recovery system. A separation system separates carbon dioxide from ambient air prior to liquefaction during operation of the liquid air energy storage system, and separates carbon dioxide from the cooled exhaust stream during operation of the combustion engine prior to emission of the cooled exhaust stream to atmosphere.

Abstract: A gas turbine engine for an aircraft includes a staged combustion system having pilot fuel injectors and main fuel injectors. The gas turbine engine further includes a fuel delivery regulator arranged to control delivery of fuel to the pilot and main fuel injectors, and a fuel characteristic determination module configured to determine one or more fuel characteristics of the fuel being supplied to the staged combustion system. A controller is configured to determine a staging point defining the point at which the staged combustion system is switched between pilot-only operation and pilot-and-main operation, the staging point being determined based on the determined one or more fuel characteristics, the controller being configured to control the staged combustion system according to the determined staging point.

Abstract: A gas turbine engine includes a staged combustion system having pilot fuel injectors and main fuel injectors. A fuel delivery regulator controls delivery of fuel to the pilot and main fuel injectors, receives fuel from a first fuel source containing a first fuel having a first fuel characteristic and a second fuel source containing a second fuel having a second fuel characteristic. In a transition range of operation between the pilot-only and the pilot-and-main ranges of operation, fuel is delivered to both the pilot and main fuel injectors at a transition staging ratio different from the pilot-and-main staging ratio. The fuel delivery regulator delivers fuel to one or both the pilot and main fuel injectors during the transition range of operation having a different fuel characteristic from fuel delivered to one or both the pilot and main fuel injectors during at least part of the pilot-and-main range of operation.

Abstract: A gas turbine engine has a combustor with a combustion chamber and a plurality of fuel spray nozzles including a first subset of nozzles and a second subset of nozzles. The first subset of nozzles are supplied with more fuel than the second subset of nozzles. A ratio of the number of nozzles in the first subset to the number of nozzles in the second subset is in the range of 1:2 to 1:5. A method includes providing fuel to the one or more fuel-oil heat exchangers, transferring heat from oil to the fuel, and providing the fuel from the one or more fuel-oil heat exchangers to the fuel spray nozzles. Heat is transferred from the oil to the fuel to lower a viscosity of the fuel to 0.58 mm2/s or lower on injection of the fuel into the combustion chamber at cruise conditions.

Abstract: A method of operating a gas turbine engine; the gas turbine engine includes a combustor. The combustor includes a combustion chamber and a plurality of fuel spray nozzles configured to inject fuel into the combustion chamber. The plurality of fuel spray nozzles includes a first subset of fuel spray nozzles and a second subset of fuel spray nozzles. The combustor is operable in a condition in which the first subset of fuel spray nozzles are supplied with more fuel than the second subset of fuel spray nozzles. A ratio of the number of fuel spray nozzles in the first subset of fuel spray nozzles to the number of fuel spray nozzles in the second subset of fuel spray nozzles is in the range of 1:2 to 1:5. The method includes: providing fuel to the one or more fuel-oil heat exchangers. Also provided is a gas turbine engine for an aircraft.

Abstract: A gas turbine engine for an aircraft, including: staged combustion system having pilot fuel injectors and main fuel injectors, staged combustion system being operable in pilot-only range of operation and pilot-and-main range of operation; and fuel delivery regulator arranged to control delivery of fuel to pilot and main fuel injectors. Fuel delivery regulator arranged to receive fuel from a first fuel source containing a first fuel having a first fuel characteristic and a second fuel source containing a second fuel having a different second fuel characteristic. The fuel delivery regulator is arranged to deliver fuel to the pilot fuel injectors during at least part of the pilot-only range of operation having a different fuel characteristic from fuel delivered to one or both of the pilot and main fuel injectors during at least part of the pilot-and-main range of operation. A method of operating a gas turbine engine is also disclosed.

Abstract: This invention concerns a fuel delivery system for an aircraft engine, comprising a fuel delivery regulator configured to receive fuel from a plurality of fuel sources for supply to the engine. An engine operating condition sensor reading is received by a control unit configured to control operation of the regulator. The control unit is configured to actuate the regulator based on a received signal from the engine operating condition sensor in order to vary the volume of fuels from the plurality of fuel sources supplied to the engine during at least a portion of a cruise phase relative to a further portion of an aircraft flight. The different fuels may comprise kerosene and an alternative fuel, such as a biofuel.

Abstract: There is provided a method of operating a gas turbine engine including a combustor. The combustor includes a combustion chamber and a plurality of fuel spray nozzles configured to inject fuel into the chamber. The nozzles include a first and second subset of fuel spray nozzles. The combustor is operable in a condition wherein the first subset is supplied with more fuel than the second. A ratio of the number of nozzles in the first subset to the second is 1:2 to 1:5. The method includes operating the engine so a reduction of 20-80% in an average of particles/kg of nvPM in the exhaust when the engine is operating at 85% available thrust for given operating conditions and when the engine is operating at 30% is obtained when fuel provided to the nozzles is a sustainable aviation fuel instead of a fossil-based hydrocarbon fuel. Also provided is a gas turbine engine for an aircraft.

Abstract: A method of operating a gas turbine engine having a combustor having a combustion chamber and a plurality of fuel spray nozzles configured to inject fuel into the combustion chamber. The fuel spray nozzles have a first subset of fuel spray nozzles and a second subset of fuel spray nozzles. The combustor is operable in a condition in which the first subset of fuel spray nozzles are supplied with more fuel than the second subset of fuel spray nozzles. A ratio of the number of fuel spray nozzles in the first subset of fuel spray nozzles to the number of fuel spray nozzles in the second subset of fuel spray nozzles is in the range of 1:2 to 1:5. The method includes providing a fuel to the plurality of fuel spray nozzles having a calorific value of at least 43.5 MJ/kg. A gas turbine engine can be for an aircraft.

Abstract: A method of operating a gas turbine engine including: a combustor arranged to combust a fuel; and a fuel management system arranged to provide the fuel to the combustor, wherein the fuel management system includes two fuel-oil heat exchangers through which oil and fuel flow, which are arranged to transfer heat between the oil and fuel and include primary and secondary fuel-oil heat exchangers; a fuel pump arranged to deliver the fuel to the combustor, wherein the fuel pump is located between the heat exchangers; and a recirculation valve located downstream of the primary heat exchanger, the recirculation valve arranged to allow a controlled amount of fuel which has passed through the primary heat exchanger to be returned to the inlet. The method includes selecting one or more fuels such that the calorific value of the fuel provided to the gas turbine engine is at least 43.5 MJ/kg.

Abstract: The present application discloses a method of determining one or more fuel characteristics of an aviation fuel suitable for powering a gas turbine engine of an aircraft. The method comprises: determining, during use of the gas turbine engine, one or more exhaust content parameters by performing a sensor measurement on an exhaust of the gas turbine engine; and determining one or more fuel characteristics of the fuel based on the one or more exhaust parameters including the nvPM content of the exhaust. Also disclosed is a fuel characteristic determination system, a method of operating an aircraft, and an aircraft.

Abstract: The present application provides a method of determining one or more fuel characteristics of an aviation fuel suitable for powering a gas turbine engine of an aircraft. The method includes: passing UV-visual spectrum light through the fuel; measuring a transmittance parameter indicating the transmittance of light through the fuel; determining one or more fuel characteristics of the fuel based on the transmittance parameter; and communicating the one or more fuel characteristic to a control module of the gas turbine engine or the aircraft. Also disclosed is a fuel characteristic determination system, a method of operating an aircraft, and an aircraft.

Abstract: A method of determining one or more fuel characteristic of an aviation fuel suitable for powering a gas turbine engine of an aircraft is disclosed. The method includes: determining, during use of the gas turbine engine, one or more contrail parameters related to contrail formation by the gas turbine engine. The determining of the one or more contrail parameters includes performing a sensor measurement on a region behind the gas turbine engine in which a contrail is or can be formed. The method also includes determining one or more fuel characteristics of the fuel based on the one or more contrail parameters. A fuel characteristic determination system, a method of operating an aircraft and an aircraft are also disclosed.

Abstract: A aircraft gas turbine engine and operation method, the engine including: a staged combustion system having pilot and main fuel injectors, and operates in a pilot-only range wherein fuel delivers to pilot fuel injectors, and a pilot-and-main operation range wherein fuel is delivered to at least the main fuel injectors. The engine further includes a fuel delivery regulator to pilot and main fuel injectors, which receives fuel from a first and second source containing fuels each with different characteristics. The staged combustion system switches between pilot-only and pilot-and-main range operation when in steady cruise mode, the mode defining a boundary between first and second engine cruise operation range. The fuel delivery regulator delivers fuel to pilot fuel injectors during at least part of the first engine cruise operation with different fuel characteristics from fuel delivered to one or both pilot and main fuel injectors the second engine cruise operation range.

Abstract: A power system for an aircraft comprises a gas turbine engine, arranged to burn a fuel in a combustor so as to provide power to the aircraft; a plurality of fuel tanks arranged to contain fuel to be used to provide power to the aircraft; and a fuel manager. A first fuel tank of the plurality of fuel tanks is arranged to contain a first fuel, and a second tank of the plurality of fuel tanks is arranged to contain a second, different, fuel. The fuel manager is arranged to store information on the fuel contained in each fuel tank and to control fuel supply so as to take fuel from the second tank for engine start-up, before switching to the first fuel tank.

Abstract: An aircraft has first and second fuel sources containing fuels with different characteristics, and one or more gas turbine engines powered by the fuels and each having a staged combustion system having pilot and main fuel injectors and being operable in pilot-only and pilot-and-main ranges of operation. The gas turbine engines each have a fuel delivery regulator arranged to control fuel delivery to the pilot and main fuel injectors. The method includes: obtaining a proposed mission description; obtaining nvPM impact parameters for the gas turbine engines, the impact parameters being associated with each operating condition of the proposed mission; calculating an optimised set of one or more fuel characteristics for each flight condition of the proposed flight defined in the flight description based on the nvPM impact parameters; and determining a fuel allocation based on the optimised set of one or more fuel characteristics.